Authentication at the zerorpc level

[guy881]

I implemented authentication at the level of the zerorpc. It is done by using a middleware both on a client and a server side. It computes a signature for every event. It involves providing a kind of secret key, which needs to be passed both to supervisor and multivisor config. I added an example to the README.md.

Although this authentication is not required, I am aware that this is an important change, I am open for discussion about improving this solution.